What’s the difference between m20 and c20 grade concrete?

A concrete of Grade C20 means that the concrete will have a compression resistance of 20 N/mm² per square millimeter in 28 days.

Proportion for grade C20.

C20 is 1:2:4 (1 part cement, 2 parts fine aggregate, and 4 parts coarse aggregate.)

where as C20 symbolizes a Cylindrical sample in which cement, fine aggregates, coarse aggregates are mixed in such a ratio that its characteristic compressive strength is 20 N/mm² after 28 days of curing.

Fig:- Concrete specimen for testing

Generally Strength of Cylinder sample= 0.8 x Strength of Cube.

example:- M20 is equivalent to C25

M20 means the grade of concrete is defined as the minimum strength of concrete after 28 days. For the M20 Grade of concrete, The letter ‘M’ refers to the mix, and 20 represents the characteristic strength of concrete in MPa or N/mm².

The specified characteristic strength of concrete is determined for 150mm size cube at 28 days. The Characteristic Compressive strength of concrete is defined as the strength of concrete as obtained from the test result (cube) for which not more than 5% of the result will be less than the strength as given for the relevant grade of concrete.

The two types of concrete mixes are nominal mix and design mix.

Nominal mix concrete may be used for a grade lower than M20 for small construction. Nominal mix grades of concrete such as M15, M20, M25 are general used. For example, M20 ratio, mix proportion will be 1 : 1.5 : 3 for 1cement : 1.5sand : 3coarse aggregates.

Design mix concrete: The property of aggregate vary from place to place, therefore adopting the appropriate properties as obtained from the standard test. The proportion of the mix (cement: fine aggregate: coarse aggregate) including water-cement ratio. The mix is designed to achieve the strength of concrete required. Large structures have high strength requirements, they go for higher grades of concrete such as M30 and above. The mix proportion of this grade is based on mix design.

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